The present Invention relates to an apparatus for treatment of Mxc3xa9nixc3xa8re""s disease and similar conditions by producing variations in positive air pressure, which are transmitted to one of the ears of a patient.
Mxc3xa9nixc3xa8re""s disease can be treated by affecting the pressure in the internal ear, in particular the endolymphatic system.
WO 83/02556 discloses an apparatus for influencing the hydrodynamic system of the inner ear comprising a displaceable diaphragm forming the wall of an air pressure generating chamber, the diaphragm being reciprocally displaceable by means of a crank coupling in a direction away from the chamber against the force of a spring coil.
WO 93/08775 discloses an air pressure generator for the treatment of Mxc3xa9nixc3xa8re""s disease by pressure pulses generated by a flexible membrane forming a wall in a pressure generating chamber, the membrane being displaced by actuation means rigidly coupled to the shaft of an electrical motor.
WO 97/23178 discloses a device for affecting the hydrodynamic system of the inner ear comprising first means for generating a static pressure level and second means for causing a variation of that level in accordance with a predetermined program controlled by a control unit. Each of the first and second means comprise a flexible membrane. Also in this known apparatus one half of the reciprocating movement of the diaphragm, the one in which the diaphragm moves towards the pressure generating chamber, is caused by spring means.
When applying square wave pulses to the internal ear in cats with a patent cochlear aqueduct a pronounced rebound effect could be noted (Transmission of Square Wave Pressure Pulses through the Perilymphatic Fluids in Cats, B. Densert et al., Acta Otolaryngol., Stockholm 1986). In humans the situation might be similar. The pressure changes in the internal ear caused by the application of square wave pulses according to methods disclosed in the prior art thus could lead to results substantially differing from what was endeavoured. This provides a possible explanation of the fact that, in spite of various apparatuses for the production and transmission of such air pressure pulses having been devised over the past fifteen years, none of them has been put into practical use at a commercial scale. This delay in the implementation of an interesting therapeutic principle seems to be due not only to these apparatuses having certain drawbacks from a constructional point of view, making them insufficiently adapted to the need of most out-patients, but also to methodological shortcomings in regard of how to vary the pressure during a treatment such as to make it applicable to a large group of patients.
The present invention seeks to overcome these drawbacks and problems, and to provide an improved apparatus for treating Mxc3xa9nixc3xa8re""s disease and similar conditions.
Other objects of the invention will become apparent from the following short description of the invention and a preferred embodiment of it, as well as from the appended claims.
The present invention bases on the insight that the forced displacement of the diaphragm in both directions, that is, towards and away from the pressure generating chamber, carries with it a number of problems, and can be advantageously substituted by a forced movement towards the chamber and a passive movement away from the chamber. One drawback with the bi-directional forced movement is the marked deviation from linearity of the spring force; another is the substantial variation of spring force within a sample of coil springs of the same kind. The incremental spring force substantially increases with the distance of diaphragm""s displacement from an idle position and translates into problems with the control of the device by the microprocessor. Another drawback with prior art devices is excess energy consumption caused by the need to work against an apparatus-inherent force in both directions of displacement.
According to the present invention is provided an apparatus for treatment of Mxc3xa9nixc3xa8re""s disease by intermittently increasing, in an air (gas) pressure chamber being in communication with an outwardly sealed external ear volume bordering to the tympanic membrane, air (gas) pressure, the apparatus comprising a peripherally fixed flexible circular diaphragm forming a wall of the chamber and being displaceable (from an idle position) in the direction of the chamber, the apparatus further comprising actuating means for displacing the diaphragm in the direction of the chamber but essentially lacking means for displacing it in an opposite direction. The movement of the diaphragm away from the chamber thus is essentially caused by the air pressure built up in the chamber and cavities communicating with the chamber. By xe2x80x98essentiallyxe2x80x99 is meant that the generation of small resilient forces on displacement of the membrane (diaphragm) according to the invention towards the chamber in an open state is negligible in comparison with the resistance experienced in a corresponding displacement with the chamber in a closed state; in this context xe2x80x98closed statexe2x80x99 refers to the chamber being in communication with the the outwardly sealed external ear volume but not with the atmosphere, while xe2x80x98open statexe2x80x99 refers to the chamber being in communication with the outwardly sealed external ear volume and with the atmosphere, for instance by of an open valve.
By xe2x80x98negligiblexe2x80x99 is meant that the force required to displace the diaphragm by a given distance, such as a distance of about 5 mm, towards the chamber with the chamber in a closed state is at least 5 times greater that the force required for a corresponding displacement with the chamber in an open state, preferably at least 10 times greater.
In other words, the design of the diaphragm should be adapted to avoid, up to the desired maximum displacement, the generation of substantial resilient forces. It is thus preferred for the diaphragm to be displaceable (from an idle, neutral position) towards the chamber essentially without being tensioned.
It is also important that combined mass of the displaceable elements of the apparatus of the invention, that is, the diaphragm and the elements coupled to the diaphragm to make it move towards the chamber, is kept as small as possible. This contributes to the apparatus of the invention saving energy in comparison with devices known in the art which is of advantage in particular for battery driven mobile apparatus.
Preferably the actuating means comprise linear electromagnetic displacement means.
According to a first preferred aspect of the invention the apparatus comprises one or several or: pressure sensing means for monitoring the gas pressure in the chamber; pressure equalising means for equalising the air pressure in the chamber with ambient air pressure; control means comprising a microprocessor, for controlling the displacement of the diaphragm and the pressure equalising means by signal input from the pressure sensing means.
It is preferred for the pressure equalising means to comprise valve means. It is preferred for the valve means to be in an open (equalising) position except during the generation of pulse trains. Particularly preferred are silent valve means working below a sound pressure level of 20 dB, in particular valve means provided with sealing faces comprising a resilient polymer. Also preferred is to control the pressure equalising means in a way such as to reduce valve noise, in particular by opening the valve slowly at the end of a pulse train and closing the valve slowly before the start of a pulse train, for example by making the opening and closing to comprise from about 0.5 seconds to 1.5 seconds, typically about one second, when going from the fully closed position to the fully opened position and vice-versa.
It is preferred for the diaphragm actuating means to comprise an elongate actuating member having an axis and being fixed to the diaphragm at its one end and, preferably at its other end, to a ferromagnetic core, an electric coil (solenoid) for displacement of the core along said axis in the direction of the chamber; means for energising the coil controlled by the control means. These diaphragm actuating means thus displace the diaphragm by a linear unidirectional force caused by an electromagnet. The coil is energised by pulse modulated 0-12 V DC. The voltage/generated force (pressure) ratio of the coil, that is, the coil voltage/diaphragm displacement ratio is about constant within the working range of the invention. The same is true for the pressure/diaphragm displacement ratio.
According to a second preferred aspect of the invention the pressure in the pressure chamber is increased from ambient pressure (p0) to a first level (p1) above ambient pressure and from there (p1) repeatedly increased to a second level (P2) and decreased to the first level (p1) again, and, following said repeated increase and decrease, the pressure is decreased from the first level (p1) to ambient pressure (p0). Preferably p1 is from 4 to 16 cm H2O, P2 is from 8 to 16 cm H2O, with the proviso that p1 less than P2, the pressure increase rate is from 0 to 4 mm H2O per millisecond, the pressure decrease rate is from 0 to 2 mm H2O per millisecond, the modulation frequency is from 3 to 9 Hz, preferably from 5 to 7 Hz, most preferred about 6 Hz, the intermittent time period being from 3 to 10 seconds, preferably about 5 seconds. It is also preferred to administer, during a treatment session, two to four treatments, in particular three treatments, separated by from about 25 seconds to about 90 seconds.
To prevent the pressure to rise excessively in case of a software failure the inclusion of a hardware controlled extra safety means is preferred, breaking the current to the pressure equalising means and the pressure actuating means if the pressure in the chamber is in excess of ambient pressure by about 25 cm H2O.
On the other hand it is important not to apply a pressure which would expose inner ear structures to suction, that is, negative pressure. It is therefore preferred to provide the apparatus of the invention with a mechanical safety valve for protection of the patient against negative pressure opening at a pressure of about xe2x88x921 cm H2O; the acceptance of a slightly negative pressure is due to design requirements for such a mechanical safety valve. It is also preferred to provide the apparatus of the invention with a safety valve for protection of the patient against positive pressure opening at a pressure of about +35 cm H2O. Both safety valves are purely mechanical and not controlled by the control means.
The combined volume of the chamber and the conduit can be varied within a broad range but considerations of design and conditions of use suggest the combined volume to be preferably from about 20 cm3 to about 50 cm3. It is important to adapt the effective area of the diaphragm to the combined volume and the outwardly sealed ear volume so as to keep its displacement below 5 mm, preferably within a range (working range) of below 3 mm for effecting the pressure variations according to the invention; this includes potential extra displacement caused by minor leakage which the apparatus is able to compensate for, and by the compliance of tissues bordering to the outwardly sealed ear volume. Typically the effective diaphragm area is in the range of from about 3 to about 8 cm2. For a combined volume of 30 cm3 an effective diaphragm area of 5 cm2 was found to be appropriate. xe2x80x98Effective diaphragm areaxe2x80x99 is the area of the displaceable portion of the diaphragm 4, including its central portion 32 clamped between elements 35,36.
According to a preferred aspect of the invention it is preferred to store, in an E2PROM (electrically erasable and programmable read-only memory) or a functionally equivalent device coupled to the microprocessor, the information for control of the apparatus in form of parameter sets, each set comprising all parameters necessary to carry out a treatment, that is, the variation of pressure in the chamber with time during treatment. It is preferred to provide the apparatus of the invention with input means to allow a parameter set to be replaced by another set. Input means not requiring an electrical connection, such as infrared (IR) input means, are preferred. The various parameter sets are stored in a computer, for instance a PC, and transferred therefrom to the apparatus of the invention. It is also preferred to store several parameter sets in the E2PROM or a functionally equivalent device, and to provide the apparatus with means for their individual selection. Thus the software for controlling the apparatus invention comprises a fixed portion stored in the PROM of the microprocessor and an exchangeable portion stored in an E2PROM or other suitable storage medium.
In the following the invention will be explained in more detail by reference to a preferred embodiment illustrated in a drawing. The embodiment is however only provided as an example and must not be considered to limit the invention in any way.